The basic helix-loop-helix transcription factor family in Bombyx mori

The basic helix-loop-helix (bHLH) proteins are a superfamily of transcription factors that play important roles in a wide range of developmental processes in higher organisms. bHLH family members have been identified in a dozen of organisms including fruit fly, mouse and human. We identified 52 bHLH members in silico in the silkworm genome. Phylogenetic analyses revealed that they belong to 39 bHLH families with 21, 10, 12, 1, 7 and 1 members in groups A, B, C, D, E and F, respectively. Genes that encode ASCb, NeuroD, Oligo, MyoRb, Fig alpha and Mad were not found in the silkworm genome. The present study provides important background information for future studies using the silkworm as a model system for insect development. Besides, the in-group phylogenetic analysis was demonstrated to be effective in classifying identified bHLH sequences into corresponding families, which can be helpful in the classification of bHLH members of other organisms.